Process of treating lead.



c. ELLIS.

PROCESS OF TREATING LEAD.

APPLICATION FILED lULY31| 191l- 1 1M 17? V Patented June 1, 1915.

Wflmwssw. v Kwkm CARLETON ELLIS, OF MION'IICIILIAIR, NEW JERSEY, ASSIGNOR '10 ELLIS-FOSTER COMPANY, A CORPORATION OF NEW JERSEY.

PROCESS OF TREATING LEAD.

To all whom it may concern:

Be 1t known that I,-CARLETON ELLIS, a

citizen of the United States, and a resident This invention relates to a method of comminuting metallic lead or similar metal to form a product especially adapted for preparing pigments such as white lead.

Inthe so called quick processes for the production of white lead, various means have been employed for reducing the lead k to a finely divided state prior to acting upon it with those reagents which bring about its conversion to white lead. Molten lead for example is granulated by pouring it into water or comminuting by means of a jet of steam or air or inert ases, or by forcing through very small ori ces so as to produce a fine lead wire.

In this finely divided condition lead is converted into white lead with more or less ease partly dependin upon the surface 'condition of the metal a ter comminution. Under certain conditions apparently it is possible to cause the surface of the lead particles during theprocess of comminution to become coated with an oxid which has acatalytic action as regards the subsequent reactions which bring about the conversion to white lead. In .many cases however the surface of the lead seemingly becomes coated with a resistant material which protects thelead particles from corrosion during the operation of conversion to white lead so that theprocess of conversion is greatly retarded and the final product often is-not pure white in color but is more or less creamy dependingonuthe amount of the unconverted or partly converted material.

The present invention involves the pro duction of comminuted lead preferably substantially free from superficial om'dation, or

in a condition readily susceptible to the action of the reagents employed in the conversion of lead to-white lead so that this operation may take place rapidly and-completely. The comminuted' lead derived in this manner is of such a character that it is particularl adapted for the manufacture of white lea by those processes employing merely air, moisture and carbon dioxid for the Specification of Letters Patent.

' Patented June i, was.

Application filed July 31, 1911. Serial No. 641,606.

conversion so that costly reagents such as acetic acid and the like are not necessarily required.

In comminuting the lead it is'desirable to have the molten lead brought to a supermolten state i. e. to a temperature of 400 or 500 above melting oint- Also it is desirable in order to pro use a proper comminution or filamentation to eject the lead under considerable pressure. Ordinarily a pressure of 300 to 400 lbs. to the square inch is desirable, and this may be obtained by maintaining a column of molten lead sufiiciently high to produce aforesaid pressure. Under such a pressure the lead. passing out through the atomizing jets breaks down into very fine particles which are sub stantially free from that oxidation ordinarily developed by air or steam atomizing jets at this high temperature, and this clean filamentous lead is speciallysusceptible to the action of air, moisture and the carbon dioxid in the'treating tanksI I prefer to conduct the operation so as to 0 tain the lead in the form of short threads, fibers or filaments. It is also possible to comminute or filament the lead by centrifugal force and for this purpose the molten lead may be fed into a centrifugal at the periphery of which are orifices or nozzles through which the molten lead may pass. Under the combined action of the pressure of the deep column of the molten lead and centrifugal force the lead is ejected from the nozzles in the form of short hairs or filaments which are also readily corroded in the treating tanks.

In the accompanying drawingsa melting furnace and atomizer is shown in section.

In Figure 1 the various tanks employed for conversion are shown in elevation. Fig. 2 illustrates the centrifugal atomizer which may be employed in lieu of the angular jet atomizer illustrated in Fig. l.

The drawings show the various essential features of the apparatus in diagrammatic form.

In the drawings, 1 is a deep pot or receptacle for holdin molten lead, to which is attached the me ting pot 2. A grate 3 is placed under the melting pot 2, and the waste. gases from the fire which is carried on this grate are allowed to pass around the pressure pot 1 in order to maintain the lead at the proper degree of liquidity.

4 and 5 are small round outlets or nozzles 1.10

in the lower part of the pressure pot 1, so disposed that their tips nearly meet at a decided angle of impingement.

7 and 8 are rods controlling flow of the metal through the jets 4 and 5.

9 is a receivin tank which ordinarily should be. partly lled with water. H desired the tank may be filled with an inert as in orderto avoid traces of oxidation.

his tank is providedwith the outlet 10 which is arranged for discharge of material into the treating tank 11. The latter may be arranged in the form of a drum or tumbler operating on the journals 12. Means are provided at 13 for the introduction of air or a mixture of air and carbon dioxid. Means are provided at 14 to convey the materialfrom tank 11 into the tank 15 which is similar in arrangement to the tank 11 with an inlet 16 for the introduction of carbon dioxid. Means are also provided at 17 for the conveyance of the material from this tank to the driers 18. The tanks 11 and 15 are provided with the gas exits 19 and 20 respectively.

- In Fig. 2 a centrifugal means is very dia-- grammatically shown. This may consistof which is sufficient to produce the a drum 19 carrying the nozzles 20' and inlet for the molten lead at 21. Any suitable mechanism may be used for driving this centrifugal.

The operation of the apparatus of Fig. 1 is as follows: Pig lead or other lead material is placed in the melting tank 2, and is brought to a molten state. t overflows into the receptacle 1 and is there raised to a temperature which makes the lead sufiiciently liquid to flow readily through the atoinizers. When a depth oflead is reached proper pressure, which as stated should ordinarily be about 300 or 400,1bs. per square inch, the lead is allowed to flow through the atomizers 4 and 5 and when the two streams meet at the point of impingement the lead is'reduced to a very finely divided condition and falls into water contained in the tank 9. The lead is then drawn into the tank 11 and treated with air and moisture until more or less hydrated. It may also be treated at this point with carbon dioxid to bring about the carbonation. Sometimes however the lead material is hydrated in the chamber 11, and passed on to the chamber 15 for carbona-' tion. Carbon dioxid is introduced through the pipe 16 and the flow of gas is continued until ordinary hydrated carbonate of lead is produced. The white lead material is then dr1ed in the drying chamber 18. The minute details of the apparatus employed are not here shown and'described, but only those figures which are essential to make clear the steps involved in the process.

It will be evident that various modifications may be made in the manner of hanas to give the operation a greater degree of continuity. The lead is preferably maintained as stated at a temperature of 400 to 500 above the melting point, and should be discharged at the atomizers as hereinbefore indicated preferably at a pressure of 300 to 400 lbs. to the square inch, although under certaln circumstances even less than this may be used, and in some cases higher pressures are desirable.

While it is not necessary to make use of any chemical reagents such as acetic acid in the conversion of the lead to white lead, such reagents may of course be used if desired, but inasmuch as they add to the cost ofthe treatment, and as the lead in the particular comminuted or filamentous form derived through this operation is especially susceptible to conversion by air and carbon dioxid in the presence of moisture, such strong chemical reagents need not be employed.

In a second modification of my process the comminuted lead is coated with a very thin layer of catalytic oxid, that is an oxid in a form capable of accelerating, more or less, the subsequent hydration or carbonation reactions.

As stated, the degree of fineness of the filamentous or comminuted lead is a most important consideration. Excessive comminution to a degree double or triple that heretofore practised in the art is one of the first considerations leading to a high grade product. Ordinary impin ement of a jet of air or steam and the lilre has not been carried out in a manner alfording a product of the requisite degree of fineness. This may be due to the cooling effect of expansion of the compressed fluid jet. For example, superheated steam under high pressure, suddenl ejected through an orifice and expan ed to atmospheric pressure, falls in temperature sometimes many hundred degrees throu h absorption of heat due to exnution with a pressure jet. in lieu of initial impingement of themolten metal streams means may beprovided for heating the. ressuch for example as that afforded by an electric are formed between electrodes at or near the tip of the directing nozzle.

In the drawings a jet 6 is shown positioned near the metal nozzles 4: and 5 arranged to cooperate with the latter in the manner indicated above. In- Fig. 2 an annulus (not shown) may be placed aroundthe centrifugal comminutor in such a manner that an annular Wall or sheet of steam or air is directed against the issuing material.-

In the subsequent treatment of the very finely divided material I preferto hydrate and carbonate simultaneously as indicated and also to conduct the operation so as to' j avoid the separation of unchanged lead, but I do not wish to limit myself to this precise procedure as, if for any reason, such as the formation of special piw 1;. .11.

modifications are retgilred involving separation of lead or dc to points of hydration or carbonation such changes would not be departing from'the spirit of my invention.

What I claim is 1. In the process of making white lead the stepwhich comprises heating lead to melt same, forcing the molten product in streams into mutual impingement and in exploding the molten spray by a jet of steam.

2. In'the process of making white lead, the step which" comprises melting lead, forcing the molten metal 'into two or more streams and in causing these streams .to mutually impinge under substantial pressure; whereby the metal is comminuted.

Signed at Chesham, in the county of Cheshire and State of New Hampshire, this 27th day of July, A. D. 1911.

CARLETON ELLIS. 

